A True Monster
by Azote Xenophin
Summary: Monsters never made it to the surface. Instead, Orochimaru found them and took their souls. How will Naruto cope with being the host to the Kyuubi, in addition to multiple monster souls, and the determination of one extra human soul? Slightly Pacifist!Powerful!Smart!Naruto, Godlike!Naruto in later chapters. Stronger!Monsters less evil!Orochimaru later on. AU.
1. Kidnapped! What?

**Hello all! I know, I'm very late on updating my other story, but I couldn't write anymore of,it unless I got some other ideas out. Well, I hope you like it!**

 **Disclaimer: I don't own Naruto or any Undertale elements. They belong to Kishimoto and Toby Fox, respectively.**

Key:

"Believe It!" - Normal Speech

 _'How annoying..._ ' - Normal Thoughts

" **Pitiful.** " - Demon/Bijū/Summon/Other Powerful Being Speech

' _ **Interesting.**_ ' - Demon/Bijū/Summon/Other Powerful Being Thoughts

" **Bijūdama** ( **Tailed Beast Ball** )!" - Jutsu names

-Forest Opening- - Scene/POV change

- **Boom!** \- - SFX

A True "Monster" Chapter 1: Kidnapped! What?!

-Orochimaru's Lab-

Orochimaru frowned as he looked at his latest test subject. It had melted again. Each one had been a failure. The bodies weren't strong enough to hold that much "determination", as it was called. He needed something better, that had enough DETERMINATION to stay together after the injection.

A jinchūriki, perhaps? The bijū were supposed to have a lot of DETERMINATION. Plus their large Chakra reserves allowed for better handling of more DETERMINATION and the extra souls. Where would he get one, though. He had connections with Homura, Koharu, and Danzo, but he doubted they would be willing to give up their jinchūriki for experiments, they were invaluable to any village with one. He decided to at least request. If they said no, he could just get it through _other_ means.

-Konohagakure No Sato-

A nine-year old with blonde hair ,sky blue eyes, and whisker-like marks on his cheeks ran home as to avoid the glares coming from the villagers around him. One or two would throw a piece of trash, a rock, or even a brick or sake bottle.

Why did they hate him so much? He was Naruto Uzumaki-Namikaze, son of the Yondaime Hokage, not that anyone knew so except a select few, and jinchūriki of the Kyūbi No Kitsune. He was not aware of his parentage, or his burden as the container of the strongest Bijū. All he knew was that they hated him, and he should avoid them as much as possible, especially after dark. They were braver in the dark. And would dare to actually hurt him if he stayed out too long, he had never experienced any kind of beating more than a couple punches or cuts, but he wasn't too keen on finding out what they would do in the dark or on his birthdays. He ran into his apartment, and locked the door behind him. The landowner was one of the only people in the village that didn't hate him, besides the Sandaime Hokage and the people at the Ramen stand, Teuchi and Ayame. He sighed, his birthdays were never fun. He wished he could be a normal kid.

What made him so different from the other kids? He never did anything wrong. Suddenly there was a knock. Naruto opened the door, the villagers wouldn't knock ever, they just barged in and stole his stuff, if he was lucky they wouldn't notice him under the bed or table. Well he was known for being incredibly lucky at times. So somehow he wasn't caught very often. At the door was an ANBU with a weasel mask(The massacre happens a few weeks after this in my story).

"The elders request your presence, Uzumaki-san." Naruto was confused, the elders always disliked him, what were they up to. Now, contrary to popular belief, Naruto was not stupid, far from it, in fact. While he was not a Nara by any stretch of the imagination, he knew something was up. But, they wouldn't hurt him, to risk angering the Sandaime, would they? He decided to play it dumb and go along.

"Yes Weasel-san."

He knew Weasel well, after a mob tried to hurt him and Weasel intervened, they would talk, and Weasel was the only one aware that Naruto was not really an idiot. He had fooled everyone else, even the Sandie himself. When Naruto arrived at the Hokage Tower, he noticed that the Sandaime was not in his usual position. He then remembered that he had gone to Suna as a liaison for a treaty with them. He was surprised when he came into the council room to find the two of the three elders smiling slightly at him, this confused him greatly.

He expected no reaction out of Danzo, but he actually was frowning a bit. Strange.

"Hello Naruto. How are you?" Koharu started. Now this was freaking peculiar. Koharu saying a friendly hello? To him? They hated his guts! Suspicious, he replied,

"I am doing well, Koharu-san."

"Well that's good. Please, come here." He stepped closer carefully. Suddenly he felt something appear behind him and his vision went black.

-Flashback, 30 Minutes Ago-

Koharu, Homura, and Danzo sat around each other as they all read the request Orochimaru gave.

"He wants the jinchūriki! Is he insane?! Not only will that severely damage our village's military power, Hiruzen will be very angry. He could have us thrown in jail for that!" Koharu shouted. Danzo, meanwhile was also upset, but for different reasons entirely. _'I_ f _he takes the jinchūriki, I will not be able to make him my weapon, but if we don't let him, he might take his anger out on Konoha, and then take the Kyūbi by force. We might not have another_ choice. _'_

After a large debate, it was decided. Naruto would be handed over to Orochimaru. They would make it look like a murder. A shinobi would be framed for murder of Naruto, and implanted with memories of doing so. The Shinobi was disposable anyway.

-Flashback End-

-Otogakure-

As Orochimaru waited for a response, he reflected on the last two months and what had happened since then.

-Flashback, Two Months Ago-

Orochimaru waited on the outside of a mountain. He had felt a Chakra surge a few hours ago, and looked to find what was causing such a disturbance. He tensed when he saw a shadow appear, he quickly hid behind a rock and masked his chakra.

The shadow was a… goat? Others appeared quickly. Two goat-like creatures, a walking fish, a dinosaur wearing a labcoat, a short skeleton, a tall skeleton, and a... small child? Very strange. He watched as they commented on the sun as if they had never seen it before, perhaps they had not. The human child stayed silent the entire time except for a single question. To be the ambassador between humans and monsters.

He would not let that happen. He could use the monsters for experiments. As the tall skeleton left, Orochimaru quickly knocked him out before he could alert the others. Then the small skeleton went inside the mouth to the Cave. He would have to get him later. The fish and then the dinosaur came. He took out both quite easily, though the fish struggled more than the lizard. The buff, obviously male goat left as well. He was harder to take than the others, but fell all the same. He had to fight seriously for that one. Then finally, the human and the last goat creature walked through. The human was easy, very weak. The second goat creature, however was almost as difficult as the first, though she seemed more reluctant to injure him, even after he initiated the battle. He soon went into the cave to gather whatever monsters were left inside.

The others were pretty easy except for two. Apparently the ones he took down were called boss monsters. These other ones were just normal. The two that gave him trouble were a strange robot of sorts and the small skeleton. The robot was relatively at The same level as the fish, which apparently was named Undyne. The robot's name was Mettaton from the TV show he saw around. The skeleton, Sans, gave him the most trouble. He had to shed his skin multiple times. (Yes, I know that he's supposed to be really hard and shit, but even with monsters stronger, he only has one hit point(supposedly) and Orochimaru is a Sannin, with the ability to shed his skin to escape dying)

Later, he walked around the Underground, weary and a little low on chakra from all the battles. He read the monster's history from tablets on the wall. He felt a little bad for doing this, but no time for pity now. He _was_ Orochimaru after all. He was able to learn the names of all the monsters, as well as their abilities. He then made his way back to his base to recuperate.

-Flashback End-

The first week was spent recuperating from the battle. And the rest of the month and half of the next month was spent studying the monsters' bodies. The last two weeks we used to experiment with the souls. Suddenly, Orochimaru was broken from his thoughts by a messenger snake, one of his summons, popping into existence. He read the scroll it held and smirked. He may have finally gotten his ultimate weapon.

-Orochimaru's Hidden Lab-

Naruto awoke in a strange cell. Holding his head, he contemplated what happened and where he was. He then remembered the meeting with the elders. Those damn elders! Now he was in a prison of sorts. He felt a little weird, as if something had changed in his body.

Overlooking the feeling for now, he searched the cell. It was completely made of steel, impossible to break as he was. Suddenly the door to the cell opened, and in came a boy with silver hair and glasses, carrying a plate of food and water.

"Hello, Naruto-san, it seems you are awake and doing well. I am Kabuto, and I will be the one to train you for these next three years. Now eat and then I will take you out to train." Training? Where exactly was he? Why was someone going to train him? He decided to dismiss the thought in favor of sating his hunger. He sat down and began to eat.

-Chapter End-

 **Yay done with the first chapter! Hope you all like it. Be sure to R &R. Any constructive criticism helps the story progress and become better. More on Sans versus Orochimaru next time! Thanks!**


	2. ET Arc: The Pain Just Keeps On Coming!

**Well, this got more popularity than I thought it would in just a couple months! I really appreciate the support you guys give me on this site. Well let's move on to some reviews!**

 **XxOmNiPoTent PriMorDial GodxX: Yes, I noticed there were no stories like this so I decided to do one. I hope my mediocre writing skills will please people to an extent.**

 **Zero: The human is Frisk, and Frisk is male in this story. I have never seen so far a NarutoXFem!Chara pairing as of yet. I may perhaps pair Naruto with a female Chara, if I can make up some crap about how she could find a host body or something, like Edo Tensei or Rinne Rebirth. We'll see.**

 **Cf96/Pikadrew9000/WingDingsGaster: Thanks. I really enjoy seeing people actually like my stories. It's just amazing to see.**

 **KHR-Yunalesca: Yes. I'm glad you think this is interesting. I had some trouble being able to write Orochimaru with a conscience as well. The Sans VS. Orochimaru will be a little hard to imagine seeing as they are from differing worlds with differing definitions of powerful.**

 **I am not going to make Kurama good right off the bat, just have him help Naruto when he really needs it, or keep him from dying. Naruto is smart, so he will piece together things quickly, and accept things rather quickly as well, so I won't take much time on having them try to get used to each other. I will not completely dismiss it, however.**

 **As for the errors, well let's just say my parents drilled correct grammar into my head, yet I do make many stupid mistakes, but I usually try to go back and look over it to check for errors.**

 **Austin 'SirAuruda1st' Bass: Yes, of course, I'm trying to at least update this one more than I did Double Nightmare, as I've now dubbed the story.**

 **King of the shadows: Thanks! Actually, I hadn't intended for this story to be for the challenge, I was going to have another story where the Uzumaki's ancestors were half-monster, and Kurama unlocked that part of him. But, I could use this one for the challenge, though you did say the monsters' powers was supposed to be part of Naruto's bloodline. About the other stuff, would you mind if it was no pairing? Just asking. If I do do a pairing, it will probably be NaruHina or NaruHinaFem!Chara.**

 **Thank you again for all the support just in the first chapter! Now, onto the story!**

A True "Monster" Chapter 2: Experiments and Training: The Pain Just Keeps Coming!

-Naruto's Cell-

As Naruto ate, he noticed the bare cell was dirty with blood, grime, and other substances he probably didn't need to know about. He still felt that foreign sensation, it covered his whole body. It was uncomfortable, yet at the same time, comforting. After a few hours of contemplating the feeling, as well as exactly where he was, the same boy from before came in, and ushered him out of the cell.

"Hello again, come outside to begin your training." Training, what? Why was he training, wasn't he a prisoner?

He calmly walked outside pondering these thoughts. He was now in a green field with a few obstacles and trees on the opposite side he was standing.

The silver-haired boy was already there. "Good, you're here. Time to start." Before he could object, the boy drew a kunai and flew it at him. Out of sheer reflex, he dodged, narrowly escaping death. His encounters with the villagers helped hone his senses.

The boy continued throwing them at him, forcing him to dodge each time. After a couple hours, he began to feel tired. Then, a kunai came speeding towards him. He was too tired to dodge or block, and closed his eyes in fear.

Suddenly, a clang sounded. Opening his eyes, He found the kunai imbedded in the wall by a bone. Surprised, he turned to the boy, who was smirking.

"Good, you've unlocked your ability." Ability? This day just got weirder and weirder.

"You must be confused. That foreign presence you feel is the ability that you just used. It was injected into you by Lord Orochimaru." Orochimaru was behind this? He heard of the criminal who betrayed Konoha. What would a Sannin want with him?

And why and how was he given this ability? He wasn't a master in biochemistry, but he was pretty sure that DNA didn't work like that.

And the only clan he knew of that could use bones as a weapon was the Kaguya clan, and they were all wiped out. Weren't they?

He was awakened from his thoughts by the silver-haired teen.  
"Well, we will continue your training right after we go through a list of what your training regimen will consist of." And the boy went inside, Naruto following after him.

-Next Week-

He grunted as he blocked the chakra scalpel of Kabuto, as he had learned the boy's name was. Everyday, he would eat, then spar with either Kabuto or Kimimaro, the last Kaguya and one of Orochimaru's most trusted soldiers.

Then, he would read on subjects from history of the Elemental Nations, to Medical information, to Ninjutsu and Taijutsu, as well as Bukijutsu, Kenjutsu, Genjutsu, and Kinjutsu.

He had improved quite impressively with his ability to manipulate bones, given the amount of time he had trained in it.

He had learned he could also use orange and blue bones, an ability the Kaguyas did not possess. Blue would not hurt you if you didn't move. Orange ones damaged anything idle.

He also learned that every time he entered a battle, everything would fade to black and white, except his SOUL, as Kabuto had called it, which was yellow.

All objects in the background disappeared for the most part, and he could only focus on the enemy.

He also discovered that he harbored the Kyuubi, and about his true heritage. A quite shocking revelation. It wasn't too subtle, now that he mulled over it. He had yellow hair, blue eyes, his parents died the day of the attack. And his last name was Uzumaki, the last name of Kushina Uzumaki, the wife of Minato Namikaze, the Yondaime Hokage, who was also expecting a child the night of the Kyuubi attack, the exact day he was born.

The Jinchuuriki thing wasn't too hard to believe, either. Considering the villagers called him "Demon brat" or "Murderer." They glared at him and hated him, threw bottles or bricks at him, and did everything they could to make his life miserable.

It made sense, they were afraid of the power he held, yet hated it because of the damage it did to the village, and the people it killed, and they needed a scapegoat. That scapegoat was to be him, because of the circumstances.

He focused back to the battle at hand, as he blocked another attack from Kabuto with his katana. He then tried to sweep out Kabuto's feet from under him, but the silver-haired teen jumped up and then tried a kick to Naruto's face.

Said boy barely ducked under it and kicked up toward Kabuto, who was still suspended in the air. Kabuto blocked with his scalpel and pushed Naruto away. Kabuto stopped, and said,  
"Well, I think that's enough for today. I will inform Orochimaru-sama of your progress to see if you're ready for the next experiment."

He figured this meant getting another bloodline to use. It was cool, but he didn't want to rely solely on bloodlines, even many different ones. A good ninja is good in all his skills, and perhaps can excel in a few given areas.

He was led back to his cell by a random Oto Chunin. He sat down to meditate a little. It helped him to concentrate and calm down.

-Orochimaru's Office-

"Hmm… I see. Naruto-kun certainly has excelled at his bloodline in such a short time. Thank you Kabuto." Orochimaru remarked.

" Prepare the next test."

"Yes, Orochimaru-sama." He replied. Kabuto walked out of the office and headed down a corridor, though he could still hear mumblings from a certain snake-related Sannin about "cursed paperwork."

He opened a secure steel vault door to reveal a lab of sorts with all kinds of vats and flasks of unknown chemicals.

He lifted one up and put it in a surgical needle. It had a bluish green hue to it. On it was a label, "Undyne."

 **Well, that's all for this chapter, tune in next time to see Naruto gain Undyne's abilities. Sorry it's a little shorter. I didn't want to introduce the next set of abilities 'till next chapter. I also will have to postpone the Orochimaru/Sans fight for next chapter, I couldn't find a place to put it in this chapter without putting the next set of abilities in the chaoter. Hope you enjoyed this installment, and I apologize if I took too long to update. Thank you, and, as always, I will see YOU in the next chapter. Bye-bye!**


	3. ET Arc: The Next Injection

**Hello, everyone. Sorry it took so long. I had a lot of stuff to do, and then i got sick for a while. But, now i'm finally doing this, and with that being said, let's get riiiiight into the reviews!**

 **mewmew99: Thank you and don't worry, I plan on updating this story for a long time.**

 **Ender the multiverse Detective: Thanks! It's always nice to have someone say your writing is good, so thank you.**

 **READER1O1O: Both of these are good ideas, I like them alot. I am leaning more towards your first idea. I might have this implemented, however, it could take a few chapters to come up with the best way to go about it.**

 **XxOmNiPoTent PriMorDial GodxX: Not quite. Good guess though.**

 **Remzal Von Enili: Sounds weird, but is an interesting idea. However, other than the unlimited chakra storages, and instant regeneration(Which he has on a lesser level anyway), I don't see the need to use it. Besides, when you use Edo Tensei, the Reincarnated soul completely takes over the body, rewriting it's personality, traits, chakra network, and kills the host when the technique ends.**

 **Cf96: Thanks!**

 **Frozem: Well, here it is! Thanks for the review and using google translator. That makes it a lot easier for me and everyone else.**

 **Stallion6 of Deviantart: Right now!**

 **Ivanganev1992: Don't worry, Naruto will know about them soon. And, if Naruto does escape, though not likely for a while, he would be pretty angry at the council, but, then again, that might get him angry enough to stay with Orochimaru to destroy Konoha, as long as certain people he cares about are left alive.**

 **Chara dreeamur storyshift: Do not fret, my friend. I plan on continuing this story for a long time, even if my updates are few and far in-between.**

 **Thanks to everyone who reviewed! It's great to see support, and that people are getting enjoyment out of my story.**

A True "Monster" Chapter 3: The Next Injection, and Sans VS. Orochimaru!

Naruto awoke in an operating room on a metal table. He noticed there were many flasks and glass containers for various liquids and pieces of DNA. Some were labeled strange names, others just had the word "DETERMINATION." He quickly got up and made his way to the door, when Kabuto came in.

" Ah. Seems you are awake, Naruto-kun." Naruto spoke,

"Yeah, what happened?"

" Well, Orochimaru-sama decided you were ready for the next injection, so we decided to give it to you. Come, we will start training with your new abilities after you eat." Kabuto responded and left. Naruto nodded and followed Kabuto out.

Orochimaru sat in his office, sighing. He unconsciously rubbed phantom pains from his fight with that skeleton. He had expected the battle to be easy. However, it was anything but that.

 _Flashback_

-Judgment Hall-

 _Orochimaru quietly followed the skeleton, which he had heard from the other was named Sans. His footsteps were silent as he shadowed the monster. Sans seemed to stop, and simply stare in front of him. Seeing him stopping and distracted, he quickly threw a snake from his sleeve to the skeleton. It raced towards him silently. When it was about to hit him, six bones came up from the ground and blocked the snake, dispelling it._

 _Orochimaru was surprised that he had blocked his sneak attack, but wasn't about to show it._

" _*well, well, well, what are you doing here?_ " _Questioned the eternally grinning Sans._

" _After you, of course. I can see you have power, and lots of it. Ku ku ku ku, with such a power I could finally create the perfect vessel." Sans didn't seem visibly disturbed or concerned, other than a raise of his nonexistent eyebrow.  
_ " _*hehehehe, sorry pal. but i can't let you do that."_ _Immediately after he finished, bones materialized behind Sans and flew towards Orochimaru. With his snake-like maneuvers, he easily avoided them._

 _He was quickly forced to dodge again as more bones came in the same way. Then, Orochimaru ran towards Sans. A wall of bones again appeared to stop him. He easily jumped on top of them. However, he felt a sharp pain in his foot and looked down to see that his sandal had been drilled through and there was a purple substance leaking from his sole. He realized that the bones were covered in serrated blades, and each one was poisoned. Realizing it wasn't fatal, Orochimaru quickly got over the poison and flew toward the skeleton again. After dodging some more bone walls instead of jumping on them, he drew Kusanagi from his stomach and slashed at Sans, who hadn't moved once since the encounter. Just as the sword was about to make contact, Sans disappeared into particles._

 _This shocked Orochimaru, however his shock quickly turned to jealousy._

'Teleportation, that would certainly give me a powerful advantage.' _He thought. He suddenly sensed something behind him. He narrowly dodged a bone that would have gone straight through his skull. He got a slight cut from the bone, and a few others that grazed him. Orochimaru grit his teeth and ran towards Sans once again. He felt a rumbling in the ground and jumped high enough to reach the ceiling._

 _Bones shot out from the earth and stopped a mere foot from hitting him. The bones receded realizing they missed their target, and just as Orochimaru was going to allow himself to fall again, he was thrown to the ground by a mysterious force. He was then impaled by five bones, courtesy of the still smiling skeleton, though you could see now that his left eye was glowing blue and his other eye socket was empty._

 _Orochimaru quickly spit a new body out of his mouth and got up. Sans was surprised, but merely closed his eyes and waited. After all, he had dealt with opponents who could come back after death before. Orochimaru tried a different approach this time. He summoned a large snake with a cry of "_ _ **Kuchiyose no Jutsu!**_ _(Summoning Jutsu)" The snake quickly sped toward Sans. He was stopped when twenty bones impaled him and he was forced to dispel. Orochimaru grit his teeth again. No snake attacks then. He made a few seals and yelled,_

" _ **Katon: Goukakyuu no Jutsu!**_ _(Fire Style: Great Fireball Jutsu)" Fire quickly raced to the hooded monster. Sans was once again surprised, but simply teleported out of the way. Orochimaru sensed a bone attack coming from the ground and jumped, however found it harder to do so than usual. He felt a little weighed down by gravity. Could it have something to do with the earlier Psychokinesis attack? Orochimaru was quickly becoming frustrated at his lack of knowledge of this skeleton. He hadn't hit the monster once, and he had already been forced to use his technique once. And he felt it wouldn't be the only time he would have to use it._

" _ **Fuuton: Daitoppa**_ _(_ _ **Wind Style: Great Breakthrough**_ _)!" The Snake Sannin cried, and a massive blast of wind flew toward Sans. Once again Sans just evaded the attack. But that's what Orochimaru wanted. He quickly used Shunshin to get behind Sans and was about to strike with Kusanagi, when a giant, dragon-like skull appeared in front of him and fired a powerful laser. It hit Orochimaru dead on, and he fell to the ground with third-degree burns all over his body. Once again, he regurgitated a new body and got back up._

 _Finally getting tired of getting beaten up, Orochimaru bit his thumb and did a few hand seals. Smirking, he put his hand to the ground, and in a giant smoke cloud, Manda rose from the ground with Orochimaru on top of him. Sans widened his eye sockets and quickly created giant blue bones that spanned across the hall, and they quickly were upon Manda. Manda tried to evade it, but to no avail. They collided with him and left torn scales and poisoned him. The poison was not very effective, of course, being a boss snake summon. Quickly regaining composure, Manda questioned his summoner._

" _ **You have summoned me for such a fight, Orochimaru? I will need at least 20 sacrifices for this."**_ _With that, he slithered toward the skeleton across the room and tried to strike, but Sans quickly teleported away. Frustrated and surprised, Manda turned around just in time to see approximately twenty-five of the giant skulls facing him, all ready to destroy. With almost no warning, they all fired. Manda managed to escape a few, but was ultimately hit by the majority of the lasers. It damaged him quite a bit, forcing him back to the summoning realm._

 _Orochimaru was outraged to see his strongest summon disposed of so easily. However, his thoughts quickly changed when he saw Sans sweating quite a bit. He realized the monster was tired from summoning so many of the skulls at once. Orochimaru needed to finish this while he was still tired. He rushed towards Sans and swiped, but Sans dodged the attack and sent more blue bones toward the Snake Sannin. Orochimaru wondered what made the bones different, but had no time to think as he jumped away, but the bones continued to follow him. He went underground and evaded them again, but the bones changed direction and chased him again. With no ground left to run, he stopped and prepared himself. He was surprised however, when the bones harmlessly passed through him._

" _*it looks like you saw through my attack. oh well, i'll just try harder next time."_ _Sans sighed. Orochimaru was then lifted into the air again and slammed against the wall. Then, bones rushed him from both sides, he quickly jumped over each one, careful not to even touch them. He was picked up again, and then had to move away from bones closing in from the sides. Everything turned black suddenly. He had to jump when bones almost impaled him. Again blackness. And again jumping._

 _This repeated several times, until a circle of the skulls appeared around him. They fired one by one, he quickly had to run in a circle to avoid them, the lasers being too large to jump over, and leaving no time to slither underground. After about ten complete rounds of lasers. He was slammed against all six walls of the hall 32 times in quick succession. He was forced once again to make a new body from his mouth. He was still being held in the air with thousands of bones all around him, leaving no escape._

" _*alright, are you ready for my_ _special attack_ _?_ " _The grinning monster questioned. Orochimaru waited for the pain, for the bones to attack from every direction, impaling him a thousand times and completely destroying his body, making it impossible to regurgitate a new one. However, after a little while of no pain, the Snake Sannin looked confused._

" _*yep. that's right. it's literally nothing. and it's not going to be anything, either. heh heh heh... ya get it? i know i can't beat you. one of your turns... you're just gonna kill me. so, uh. i've decided... it's not gonna BE your turn. ever. i'm just gonna keep having MY turn until you give up. even if it means we have to stand here until the end of time. capiche?_ " _Orochimaru sweatdropped. This guy had nothing else to use against him? Now that he took a closer look, the skeleton looked very tired, and was sweating profusely. The bones keeping him from escape were shaking a bit. He tried to move towards the bones, to maybe slip through the tiny cracks. However, Sans quickly teleported him back to the center. Another attempt, the same result. Orochimaru decided to just outwait Sans._

 _After quite a bit of boring dialogue(I do not care for having Sans say everything he did in the actual fight, even if it would cause my word count to skyrocket), Sans started to fall asleep, and soon was standing there, completely unaware of his surroundings, supposedly. Orochimaru used this to escape from the bones by transforming into a snake. He then quietly walked over to Sans and made a downward slash on his form. However, to his utter shock, Sans actually dodged the attempt._

" _*heh, didja really think you would be able-_ " _He was interrupted when Orochimaru swung again and this time hit his mark. The skeleton fell to the ground, bleeding from the mouth and chest, completely mystifying Orochimaru, as this should have been impossible due to the structure of the monster._

" _*... … … so… i guess that's it, huh? ... just... don't say i didn't warn you. welp, i'm going to grillby's._

 _...papyrus, do you want anything?_ " _That made Orochimaru feel a little strange. He knew what the feeling was. Sadness. But he had not felt this or any positive emotions in years. Perhaps it had something to do with the fact that he had his own parents killed, and then he had killed the skeleton's brother? He decided not to dwell on it, quickly leaving the hall. He investigated the rest of the underground before leaving, trying to get as much information as possible on the monsters and their abilities._

 _He found the True Lab easily, as the elevator had been left open. He read through the notes of the owner, and realised he had been doing similar experiments to Orochimaru's, making them a good basis for his own research. However, unlike him, the monster was doing this to free his people, not become stronger. He also seemed to dislike doing the experiments, and had planned to let the test subjects go after a while._

 _This pulled at him for some reason or another. Was he feeling guilt, for constantly hurting people, only because he feared death? No! That couldn't be it. He buried the feeling he had, and continued to the surface. He was the Snake Sannin, the one who would master every jutsu, and learn the secret to true immortality! He had no need for petty feelings such as sadness or guilt. With these thoughts, he left the Underground and headed to his base in Otogakure no Sato._

 _(Very Long) Flashback End_

-Orochimaru's Base Of Operations-

Orochimaru sighed once again as he thought about the encounter. It just went to show how strong people in this world were. If it weren't for his special jutsu, he would have died three times in his battle with Sans. He also couldn't stop thinking about the emotions that had been wrought out by the confrontation and aftermath. He felt different than before. Could he really be feeling… sadness for the people he killed?

It didn't make sense. In all these years, he had never felt any kind of sadness or pity when using people for experiments. So why were these feelings arising now? Was it the similarity of his situations to Sans'? Or Alphys' regret and sadness over her experiments? Whatever it was, it made it hard to focus on his work. He decided to put it away so he could concentrate. And with that, he returned to work.

-Training Field,Otogakure-

Naruto was sweating profusely as he faced Kabuto. They had spent hours training Naruto's new ability to create spears made of chakra. He now had fish scales enveloping portions of his arms and neck, as well as gills. This form would also probably be able to swim underwater, but be susceptible to intense heat, meaning not a good choice if were ever to go up against heavy Katon users like the Uchiha.

Naruto now possessed the ability to throw his spears in four directions around the target which could not evade the attack, only block it, he could even use special spears that switch directions at the last second, create spears that burst from the ground, and freely fire spears at the target, but could easily be dodged if their paths were predicted. Meaning they would be good for catching opponents off guard. He might need to have some kind of seal that cools his body so he wouldn't be unable to use these abilities in a desert, or the like.

"Well, let's continue, Naruto-kun, don't just stand there." Kabuto urged. The aforementioned blonde simply nodded and created more spears to use. Kabuto jumped into the air to avoid a few that were coming from the ground, and blocked the smaller, flying ones with a kunai. The fight continued on for a while, with Kabuto dancing around Naruto's attacks, or blocking them almost effortlessly. Until finally, Naruto collapsed.

Even with his extended chakra supply and stamina, it took too much energy to use this ability, which is also why Kabuto demanded he train it, to decrease the time and chakra it took to create the spears and guide them. Kabuto walked up to the jinchuuriki and helped him up.

"Okay I think that's good for today, go rest, and we'll continue tomorrow. When you have completely mastered these abilities, you may take off a couple of days to do whatever you desire." And with that, Naruto heads back to his cell, and fell on his "bed". He knew that Orochimaru planned to steal his body, and was training him so that the muscle memory would stick. Even though he knew this, he was quite fond of Kabuto and Orochimaru, as they treated him better than the villagers ever did. He actually felt wanted here, even if it was only for his abilities and jichuuriki status. As Naruto contemplated these things, he slowly fell into a blissful sleep.

 **And we're done! Well… That took forever! I just could not think of anything for this story, I couldn't decide where to take it next. But, after staying up until 1:30 AM on some nights, I finished it! I hope to continue to the next chapter soon. I plan on giving him Mettaton's abilities next. How you ask? Well, Mettaton still is technically a monster, just a ghost monster in a robot body. He would still have some kind of a soul to extract, and his abilities wouldn't be the robot ones, rather the abilities of a ghost, so be prepared. Also in the next chapter, Konoha's status without it's Jinchuuriki! Thank you for reading! I hope to see you next time, whatever I may write, and keep reading Fanfiction. Ja ne!**


	4. ET Arc: Undyne to meet ya, Kyuubi!

**Hello everyone! I'm back again! I want to continue all of my stories, but having three stories all surrounding the same character can be a little difficult, as they start blending together. Anyway, enough about that. Onto reviews!**

 **Remzal Von Enili: Yeah, actually. Sound based attacks could be useful, and thematic, since, you know, the village Orochimaru runs is called Otogakure (Hidden Sound). We'll see where it goes. Visual sound waves might be interesting. As for the Spirit Gun, if you're talking about Yu Yu Hakusho, then I'm afraid I have yet to watch it, and I dislike going off of a wiki for things like that. I want to watch YYH, but it's in the middle of a** **Very Long** **list of anime I want to watch. And incorporating another crossover so late into the game might make it weird and make the story seem off.**

 **Drewmaster: I'm glad you think so. I think there are way too many that just do exactly what the anime did, just with a different Naruto. I try to diverge as much as possible, as hard as it is. While it will stay true to many of the anime and manga elements, this fic will be from a different perspective. If you mean a new realm like a multi-crossover, as I said before, that might make it a little more convoluted and confusing than it needs to be. I'm gonna try to stick to Naruto and Undertale.**

 **StallionWolf: Yeah, it is. You can see that Orochimaru wasn't always like he was when you first meet him in the Forest of Death. He used to be a genius with a dream, scarred by the War. But his dream developed into an obsession. I want to try to keep Orochimaru closer to human than he was originally, but not completely take his personality away. As for the Fire based magic, Naruto can only have one ability active at any given time, for now, though that could change. I would think that people with Fire Magic would have some sort of resistance to it, but Asgore seemed just as vulnerable to Toriel's fire as anybody else.**

 **Guest: I will always be updating this story until I die (actually I read a story whose author said almost exactly the same thing, and he hasn't updated that story in 5 years, is he dead? Who knows?). As for summons, he will get a summon, but you will just have to wait and see which one(s) it is!**

 **Onishin Tsukitenshi: Your prayers have been answered!**

 **PinkiePieParty122894: Wait no longer!**

 **Mewmew99: Here it is, though probably not as soon as you hoped.**

 **Wicked.A: True, but shinobi need a high pain tolerance to be effective in their job. And if a child like Frisk could somehow not be hindered by the Karmic Retribution, then I think Orochimaru will be fine. Genocide Frisk was pretty evil in their own right as well, remember. Orochimaru also isn't completely evil in this, either, he has some empathy.**

 **Junior VB: Thanks! Even such a simple review means a lot to me!**

 **Thanks everyone for all the support and reviews. I look at every review I get, even if I don't answer it in the chapters. Just simple reviews like "I liked it." or constructive criticisms about what I missed or could have done better are appreciated. So just take a moment of your time to tell me what you think, it's greatly appreciated.**

 **Disclaimer: I don't own Naruto or Undertale. I would hope you know that.**

A True "Monster" Chapter 4: Undyne to meet ya, Kyuubi!

-Konohagakure no Sato-

Hiruzen Sarutobi sighed, his aged facial features looking even more wrinkled than usual. Most likely because of the stress of finding out that Naruto was missing. He had not found out until recently and believed the elders had a hand in it. However, they denied everything, and he had no evidence to prove that they had indeed taken part in Naruto's disappearance. Shaking his head, he tried to focus on his paperwork, which was stacking up even more than normal. But he just couldn't get the boy's infectious smile out of his head, and ideas of what may be happening to him. Experiments, torture, and things he didn't even want to grace with a description.

' _Minato, you would be disappointed in what this village has become.'_ The Sandaime thought as he remembered the parties that had happened when the villagers were made aware that the blonde jinchuuriki was gone indefinitely. He couldn't really punish them for such acts, no matter how much he wanted to. With another sigh, he got to work on the dreaded stack of papers.

-Orochimaru's Lab-

Naruto awoke from his forced sleep to see Orochimaru looking at flasks and pieces of paper. He didn't even seem to notice Naruto get up and get up next to him. Naruto looked at the pieces of paper. Many of the words were difficult to understand, but he knew that they were for an experiment of sorts. Deciding he didn't really need to know what these papers were about. He hesitantly tapped Orochimaru on the shoulder, really not sure how the Snake Sannin would react. Orochimaru turned around a little quickly in surprise but calmed down a little when he saw it was Naruto.

Orochimaru gave a slight smile, though he was inwardly cursing himself for not noticing he had been there. If it were an enemy, he could have been severely injured or worse.

"Ah, hello Naruto-kun. I see you're awake. So far the experiments seem to be going well. Please go and rest, it's already late and experiments such as the ones you have been doing tend to drain the subject's energy. Kabuto will train with you on your new abilities tomorrow." Naruto simply nodded and left. Orochimaru would be lying if he said he wasn't surprised by how calm Naruto had been. He never seemed to be anxious around Kabuto or himself, or really anyone who was around him. The Sannin knew that Naruto was guarded. He was always ready to defend himself, even when alone. But he made no indication that he was disgusted by Orochimaru's actions, or that he wanted to escape. He seemed to be perfectly content living in his cell.

' _It might have something to do with how the villagers treated him when he was in Konoha.'_ It actually made Orochimaru a bit sad that the blonde was treated better in Oto, where he was being held captive, than in Konoha, where he was born as a free citizen. Jinchuuriki were hated, that much he knew, but they seemed to be even more hostile toward him more than other jinchuuriki he had observed as part of his time in Akatsuki. Orochimaru banished these thoughts that had increased ever since he had acquired Naruto. Right now he needed to focus on his work.

-Testing Room-

Naruto carefully opens his eyes, seeing Kabuto already in the room. Kabuto doesn't speak, simply walks away, motioning for Naruto to follow. They arrive at a training ground that Naruto uses quite frequently for testing his new abilities. Already used to the procedure, Naruto doesn't waste any time trying his new ability. It was strange that he could feel his ability before he even knew how to use it. It was a surprise to everyone when he used his first ability without anyone to explain it to him. He said that it was like it had always been there since he was born, yet it was still new.

The jinchuriki quickly got to work, trying to focus on the ability. After a few seconds, his skin on his arms and legs, as well as near his ears and neck turned blue and scaly. A spear formed above him. He wasted no time in trying to get it to fire at Kabuto. It took a little while, but it went on its way to the medic, albeit slowly. Kabuto easily dodged, and this time, he took the initiative and sped towards Naruto. Naruto dodged and then tried again, this time, the spear formed faster, and there were now three. They sped toward Kabuto, faster than the first time, but still not fast enough to really catch anyone above Mid-Genin. This time, Kabuto blocked the first one with a kunai, though it cut into it pretty easily, stopping just short of cleaving completely through it. He was forced to dodge the rest of them.

Naruto formed even more spears. These were much larger than the previous. They were bigger than Kabuto himself. One by one, the spears would come at him. It seemed to take too much concentration to move all of them at once. He was able to see which one would move and then acted accordingly. After a while of this, Naruto decided to try something different. He surrounded Kabuto with multiple smaller spears. They all came at him, leaving no time to dodge. He summoned a chakra scalpel and fended them off. They disappeared after hitting the silver-haired boy's weapon, but there were just too many.

He was almost caught by one before he jumped over the wave of spears and landed a safe distance away from them. Naruto formed more of the normal-sized spears, and they formed a circle around Kabuto, and slowly closed in on him while circling, to keep Kabuto from leaving too easily. He made sure that there were also ones above him to keep Kabuto from jumping. However, it was all for naught. Kabuto easily saw where he could exit and left through one of the many gaps in the circle. Naruto tried to pursue, but using his power so freely just after receiving it left a great drain on his massive chakra reserves, and he fell to one knee. Seeing this, Kabuto walked up to Naruto and offered him a hand. Naruto took it and got up.

"Quite impressive, considering you just received this power and had no idea of what it did before using it." Naruto gave a small smile. He was glad to receive praise, even if it was from people like Kabuto or Orochimaru, who only had interest in taking over his body. Here, at least he felt wanted, unlike his "home." Kabuto told him to go the library and pick up a few books that he had listed on a piece of paper. Taking the piece of paper, the blonde complied. In a world where Naruto grew up craving attention and ended up neglecting his studies, he might have complained. But this Naruto, realizing that knowledge is power, was eager to read and learn something new.

Some of the books were on history, while others were recognizing, creating, and neutralizing poisons. While the Kyuubi would take care of most poisons, you can never be too careful, in the event a poison too potent for the Bijuu came along, or the Kyuubi was unable to purge a poison from his body, it would be helpful. Some of the other books were genjutsus. For now, he didn't have enough control to cast genjutsu, other than the basic **Bunshin**. But dispelling genjutsu is crucial to a shinobi's repertoire. Naruto could detect and dispel most genjutsu under B-rank, but perfection is always strived for.

"Perfect practice makes perfect." Orochimaru would often say. So Naruto made sure that he didn't stop practicing something until it was second nature to him. After reading through most of the books with the help of his Shadow Clones, he went into his cell and meditated for a few hours. Meditating was a good pastime for him. He liked the silence and peace of mind that came with it. It was also how he first met his tenants.

 _Flashback_

 _Naruto was meditating, as was his daily routine now. Orochimaru told him to do so every day since it helps you stay in touch with yourself, and can also help you to learn to remain calm during battle. Suddenly, almost as soon as he had relaxed, he felt a sort of pull. He felt water under his feet. Using chakra to stay on top of the water, he opened his eyes to see that he was in a sewer of sorts. It seemed almost like it was going to fall apart any second. It didn't take a genius to know that he was in his mind, though why he would be escaped him. He had never heard of a person's mind taking a landscape form. A "mindscape," if you will._

 _He noticed a few pipes lining the walls and ceiling. Some blue, some two different shades of red, and some that were white. He followed the pipes, twisting this way and that, following so semblance of logic. Finally, he came to a very spacious room. Half of the room was blocked off by bars resembling Naruto's own cell's. On the bars, there was a large piece of paper that held the kanji for "Seal." The blonde immediately knew what this room was for. Moments after deciphering the purpose of the room, two frighteningly giant eyes appeared in the blackness. They were red with black slits for pupils. Naruto didn't look the slightest bit daunted, not even when a large claw slammed against the bars, passing through and just barely missing his small -in comparison to the claw- body._

" _ **Well boy, you certainly have guts. Not even flinching, huh? Don't worry. I'll get out of this seal eventually, and I'll kill you."**_ _If Naruto heard the Bijuu, he didn't show it. He simply said,_

" _Did you bring me here? I felt a pull on my consciousness." The Kyuubi growled, then smirked, or at least Naruto thought it did._

" _ **Right to the point. Well, to answer your question, yes. I figured we should at least talk. I have to say, you're pretty intelligent and strong for a boy your age. If I'm going to be trapped inside a whelp like you, then I refuse to have a weak jailor. I will assist you in certain aspects of your career. I'll dispel any genjutsu you are unable to, to the best of my ability. I'll train you to use my chakra and my techniques. I'll even let you sign the Fox contract. However, in return, I wish to have**_ _ **some**_ _**freedom. What do you say?"**_ _Naruto stood still for a few seconds. Then, he replied._

" _How much freedom are you speaking of?" The Kyuubi snorts, and answers._

" _ **I'm not asking to be actually free. Just to have access to your five senses, and maybe eventually summoning me through my contract, if it's possible."**_ _Naruto waits a few seconds again before he makes a decision. "It's a deal. However, I want a promise that you will not try to take over my body without my explicit permission -or I am about to be killed or captured- when I use your chakra, and no killing innocents if I summon you." The Kyuubi snorts again but promises anyway._

" _ **I swear on my... pride and status as the strongest of the Bijuu, that I will not take over your body without your permission unless you are in immediate danger... and I will not kill anyone you do not tell me to kill if you use the fox summoning contract to summon me."**_ _The Bijuu seemed to almost force the words out in reluctant acceptance. It seemed he desperately wanted some freedom. Naruto nodded, and also, to the Kyuubi's surprise, promised that he will release the Kyuubi before he dies, in exchange for the Kyuubi making sure that he dies of old age, rather than in combat, or the Kyuubi purposely getting him killed to be free. The Kyuubi accepted, his respect for the boy growing. When he asked why Naruto would do this, the jinchuuriki replied,_

" _You are not just a chakra construct of malice and hatred, you are a living being, with a soul, and deserve to be free. I understand that you have been sealed for many years in succession, and when you were free, it was only for the briefest of time, before being sealed again." Kyuubi was content with the boy's answer and decided to tell the boy the truth about that night. He already knew that Naruto knew about his parents, and respected them for their decision, even if he was upset that Minato failed to see an outcome like the one that had developed. He was too trusting of the village._

 _Naruto was a bit surprised to hear that supposedly Madara had controlled the Kyuubi the night of the attack and that his mother was the Kyuubi jinchuuriki before him, and before that, Mito Uzumaki, the wife of Hashirama Senju. He figured it must be their accelerated healing and strong bodies that allowed them to carry the strongest of the Bijuu. He declared that he would make Madara answer for taking away his chance at a free life, and for controlling the Kyuubi. For once, the Kyuubi was almost glad that he was sealed inside Naruto. Maybe, one day, they could work together, as friends and as comrades. But for now, they would have a strictly business relationship. Then, as Naruto was going to leave, a yell came from the darkness._

" _What the hell is that?! Where the hell am I?1?"_

 **Aren't I just terrible? Well, sorry. But I needed to stop here, I'm tired, and I can't decide if Naruto will be meeting Papyrus and Undyne, Frisk, or all three in his mindscape. Please help me out. And if you do want one or the other, try to explain at least a little bit why it would make the most sense out of all the options. Also, do you want Naruto to have access to Chakra Chains? Review and let me know on that as well, in addition to any pairings you want, though be warned, I'm not good at writing romance. You may have noticed a change in the description. I realized that hundreds of monster souls would be too much for now. Later, he may get them. But the working story for right now is that Orochimaru used the souls of the remaining monsters other than the main characters for testing on other individuals. Another thing to note, in this fic, Minato assumed that Yin and Yang should never be separated, and sealed all of the Kyuubi inside Naruto, hoping that he could handle it. Naruto did. Also, keep in mind that Orochimaru will still want to learn all jutsu in existence, and become immortal, but he has a bit of a soft spot for Naruto. Thanks for reading, and I'll see you next time.**


End file.
